Photosensitive cell



Dec. 4, 1928.. 1,694,189

s. RUBEN PHOTOSENSIT IVE CELL Filed Dec. 6, 1927 U Q A Milli-WA a k R v.1 m a la F Since/Mo SAMUEL RUBEN meme Dec, 4, 192

UNITED STATES 2 4 PATENT OFFICE.

saxtmnnuun, or new YORK, N. r.

PHOTOSENSITIVE CELL.

Application fled December a, 1921. Serial No. seam-r. 1

This invention relates a photo-sensitive cell and to the method ofmaking the photosensitive element thereof.

( The object of the invention is the provision cause of its highspecific resistance when so.

employed it must-be used in a thin layer on a supporting base.

Broadly, my invention consists of a tube evacuated to a pressure atwhich substantially no positive ionizationoccurs, and having threeelectrodes, cathode, anode and grid, the last of which comprises acopper body having on its surface a fused layer of cuprous oxide whichis made in the manner hereinafter described, and which is electricallyhighly sensitive to light ra In this device the grid is operated t rougthe intermittent exposure of the cuprous oxid surface to light raysthereby va'rylng its electrical resistance and correspondingly, its'tential, employed to va thedistribution o the electron stream over t 0plate surface, and therefore the current flow in the cathode-anodecircuit.

I have found that for most efiective photoelectric application thecuprous oxid layer on the copper base must have minimum specificresistance and maximum crystal layer density, to obtain which, by themethod of my invention, a copper body is heated in an oxidizingatmosphere to 10009 0., and when a fused cuprous oxid coating of about0.1 mm. has thus been formed on the base surface it is plun ed into a25% solution of hydroc oric aci when it forms a dense clear, red,lass-like, cuprous oxid coating which is firml y adherent to the base.It is obvious that any undesirable reaction product remaining on thesurface after the quenching of the hy-' drochloric acid should be entirey removed either mechanically or chemically In order to present thecleanest red cuprous oxide sur face ssible. This la er is chemicallypure and as'a relatively ow specific reslstance compared with that ofsuch a compound pre pared by the methods now knownas for example, byheating the copper to a high tem-',:

perature and allowing it to slowly cool in the air, when there is formed,a layer of cupric oxid outside of the cuprous oxid coating.

The outer layer has a higher resistance than the cuprous oxid and is notsatisfactory for photoelectric use.

Because of the polarized character of'the cuprous oxid layer formed,.and especially when quenched by the method of my invention, excellentasymmetrical conductivity is ,shown in a cell using this material as aseparatlng element. This factor is to be taken" into account in theelectrical connection and use of the element in a photoelectric cell.

In view of the ve -thin layer employed and of the necessity or exposingthe maximum amount of surface to the radiations to be indicated, it ispreferable to use this layer in the'form described, as in a vacuum tube,to control the flow of ionic or electronic discharge. Below I describe apreferred form of photoelectric cell utilizing the photoelectric cuprousoxide layer to control an electric discharge by resistance variations ofits surface layer responsive to exposure to light rays To minimize theefl'ect of possible radiations from a source of electron emission in adeviceof this character, there is employed a filament or electronemission cathode having as its electron emission surface a layer ofalkaline earth oxids, such as strontium and barium oxids which allowsa-cathode o 'era-' tion at a low temperature or at a dul red heat. Inthis respect the combination of a photo-sensitive resistance element anda low temperature cathode is equivalent to that cited in my rior andcopending application, bearing Serial Number 534,213.

In the accompanyin drawings, illustrative of one embodiment o theinvention, Fig. 1 shows in outline a vacuum tube equipped with aphoto-sensitive electrode and other electrodes, connected in an electriccircuit and Fig. 2 is a section view of the electrode at 22.

At 1 is a filamentary cathode coated with strontium and barium oxidesand supported by leads 1, and 1 and mounted on lead 2, edgewise to thecathode is anode 2, and extending upon two sides of and parallel withthe anode is the grid or control element 3, composed ofa copper striphaving fused on its surface a coating of light sensitive cuprous oxid.At B is the source of heat energy for e cathode, and B, is the source ofpotential tween the cathode and grid, B being the source of potentialbetween the cathode and anode and R the resistance in that circuit.

In operation, as light is impressed upon the grid element, causingchanges in its initial resistance, corresponding changes occur in thepotential in the grid circuit, in this way controlling the electronstream bombarding the anode. Thus, the cathode-anode current dischargeis varied in response to changes in the external light rays impingingupon the cuprous oxid grid coating.

What I claim is 1. In a photoelectric cell, the combination of acathode, an anode and a control electrode composed of a copper bodyhaving a surface of fused cuprous oxide.

2. The method of making a photo-sensitive electrode which consists inheating a copper body to 1000 C. while exposed to the air and quenchingit in a per cent solution of hydrochloric acid.

3. The method of producing a photo-sensitive resistance element whichconsists in heating a copper body until a fused layer of cuprous oxideis formed on its surface, and quenching it in a solution of hydrochloricacid.

e. The method of producing a photo-sensitive electrode which consists inheating a copper body in an oxidizing atmosphere until there is a layeron said body of an integrally formed homogeneous non-porous cry..-

talline compound of said copper body, and quenching it.

5. In a photo electric cell, a cathode, an anode and a control electrodeconsisting of cuprous oxide.

6. In a photo electric cell, a cathode, an

anode and a control electrode consisting of fused cuprous oxide.

7. In a photo electric cell, a cathode, an anode and a control electrodeconsisting of a metal base having an exposed surface of substantiallycuprous oxide.

8. In a photo-electric cell, a resistance control electrode consistingof a metal base having an exposed surface of fused cuprous oxide.

9. Inan electron discharge device, an element for controlling theimpedance of said device, having a surface of integrally formed,homogeneous, non-porous crystalline cuprous oxide.

10. In an electrical discharge tube, a cathode, an anode and a controlelement consistmg of cuprous oxide.

In testimony whereof, SAMUEL RUBEN has signed his name to thisspecification this 5th

